Coil spring

A compression coil spring

A tension coil spring

A selection of conical coil springs

Oxy-cut spring showing deformation due to loss of tempering in adjacent turn

A coil spring, also known as a helical spring, is a mechanical device which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. They are made of an elastic material formed into the shape of a helix which returns to its natural length when unloaded.

Under tension or compression, the material (wire) of a coil spring undergoes torsion. The spring characteristics therefore depend on the shear modulus, not Young's Modulus.

A coil spring may also be used as a torsion spring: in this case the spring as a whole is subjected to torsion about its helical axis. The material of the spring is thereby subjected to a bending moment, either reducing or increasing the helical radius. In this mode, it is the Young's Modulus of the material that determines the spring characteristics.

Metal coil springs are made by winding a wire around a shaped former - a cylinder is used to form cylindrical coil springs.

Variants

Volute spring suspension on an M4 Sherman tank

Types of coil spring are:

• Tension/extension coil springs, designed to resist stretching. They usually have a hook or eye form at each end for attachment.
• Compression coil springs, designed to resist being compressed. A typical use for compression coil springs is in car suspension systems.
  • Volute springs are used as heavy load compression springs. A strip of plate is rolled into the shape of both a helix and a spiral. When compressed, the strip is stiffer edge-on than a wire coil, but the spiral arrangement allows the turns to overlap rather than bottoming out on each other.
• Torsion springs, designed to resist twisting actions. Often associated to clothes pegs or up-and-over garage doors.

Applications

Coil springs have many applications; notable ones include:

• Buckling springs in computer keyboards
• Mattress coils in innerspring mattresses
• Upholstery coil springs in upholstery
• Coil Springs in Car Suspension

Coil springs are commonly used in vehicle suspension. These springs are compression springs and can differ greatly in strength and in size depending on application. A coil spring suspension can be stiff to soft depending on the vehicle its used on. Coil spring can be either mounted with a shock absorber or mounted separately. Coil springs in trucks allow them to ride smoothly when unloaded and once loaded the spring compresses and becomes stiff. This allows the vehicle to bounce less when loaded. Coil spring suspension is also used high performance cars so that the car can absorb bumps and have low body roll. In off-road vehicles they are used because of their range of travel they allow at the wheel.

• Coil Springs in the engine

Coil springs are used in the engine. These springs are compression springs and play an important role in lifting the valves that feed air and let exhaust gasses out of the combustion chamber. The spring is attached to a rocker that is connected to the valve.

See also

• Timmis system, an early form of coil spring used on railway axles.
• Spring (device)

External links

• Helical Spring by Sándor Kabai at The Wolfram Demonstrations Project.
• glossary by manufacturer McAllister Industries.
• Institute of Spring Technology
• Spring Manufacturers Institute
• [1], tutorial by Dave Silberstein.
• "You Spring From Morning To Night" , April 1949, Popular Science article on the basics of steel coil springs manufacturing.
• http://suspensionspot.com/springs/